1. Field of the Invention
This invention relates to a switch for switching an optical fiber from a first to a second groove in response to a switching force and, in particular, to a switch in which the switching force is imposed directly on the fiber.
2. Description of the Prior Art
Fiber optic communication systems now use either single mode or multimode optical fiber cables to transmit information within a local area network. Switches permit optical paths within the network to be changed to allow for the information to be directed to a particular unit or units or even to bypass a particular unit. Switches for such uses must exhibit a high degree of reliability over many switch cycles, low insertion loss, low crosstalk, and short switch times.
Several forms of optical fiber switches are known. In some switch arrangements the switching function is accomplished by placing an optical device within the optical path. Copending application Ser. No. 07/452147, (ED-0385), filed Dec. 18, 1989 and assigned to the assignee of the present invention, now abandonment discloses the use of a movable blocking element to switch light from one fiber to another or to an off position. U.S. Pat. No. 4,790,621 (Calaby et al.) shows the use of a movable prism to switch light from one fiber to another. U.S. Pat. No. 4,261,638 (Wagner) discloses the use of a reflecting member to switch light along different optical paths.
Mechanical switching arrangements are also known. In such devices the optical fiber is fixedly mounted to a movable member and the member is physically displaced from a first to a second position to switch the optical path. U.S. Pat. No. 4,911,520 (Lee), also assigned to the assignee of the present invention, utilizes a cantilevered glass tongue to which a fiber is edgewise mounted. A first and a second fiber are similarly mounted along edges of a fixed block. Moving the glass member from a first to a second position removes the fiber thereon from a first optical path that includes the first fixed fiber and places the fiber into a second optical path that includes the other fixed fiber.
In U.S. Pat. No. 4,407,562 (Young) optical fibers are secured in grooves disposed on the exterior surface of a movable housing. Displacement of the housing brings the faces of the fibers into and out of alignment with other arrays of fibers thereby to cause the switching action. Alignment of the movable housing with the casing in which it is disposed is effected using alignment grooves. U.S. Pat. No. 4,896,937 (Kraetsch et al.) provides two V-grooves, one in the cover and another in the base of a the housing. The switching action is accomplished by moving a ferromagnetic strip to which a fiber is attached into position in one of the V-grooves.
U.S. Pat. No. 4,759,597 (Lemonde) mounts an optical fiber to a magnetic rocker arm. The pivotal motion of the rocker arm moves the fiber between corresponding fibers secured in grooves respectively provided in an upper and a lower support slab.
In the above discussed mechanical switches the switching action is accomplished by moving, in addition to the mass of an actuating element, a member to which the fiber is attached. That member is relatively large and massive as compared to the size and weight of the optical fiber. These devices would thus appear to be limited in their switching speed.
U.S. Pat. No. 4,946,236 (Dautartas et al.) discloses a switch in which the displacing force is applied to the fiber itself. The switch includes fibers that are surrounded by a magnetic sleeve. The fibers are disposed within grooves defined by the corners of an elongated, diamond shaped, internal channel extending through a block. A magnetic field is applied to effect the displacement of the fibers from one corner of the groove to another.
In view of the foregoing it is believed advantageous to provide an optical fiber switch having a repeatably low insertion loss, a relatively short switching time in which the switching action is accomplished by moving (in addition to the mass of the actuating element) only the relatively minimal mass of the fiber.